The present invention relates to a tool extender and tool assembly and, more particularly, to a tool extender and tool assembly having guides for enhancing stability of the tool relative to the tool extender.
One technique for securing tool bits such as drill bits or milling inserts, such as ball nose end mill inserts, to chucks of drill presses or milling machines is to provide an internally threaded chuck and an externally threaded tool bit that mates with the internal thread of the chuck. U.S. Pat. No. 756,377 discloses a chuck for rock drilling machines that has an internally threaded, tapered hole that receives a split nut that can secure a tool bit when threaded into the chuck. A disadvantage to the type of device disclosed in U.S. Pat. No. 756,377 is that forces on the tool bit may be transmitted through the split nut to the threads and damage the threads, requiring replacement of the split nut and the chuck.
Adjustable chucks are common today, and typically are capable of clamping a range of different diameter tool bit shanks. Certain adjustable chucks are not, however, ideally suited for clamping all shanks. For example, Sandvik AB, Sandviken, Sweden, produces CAPTO tools in which a polygonal chuck opening is ideally suited for clamping polygonal shanks. Tool bits that have customary cylindrical shanks do not fully enjoy the advantages of the CAPTO system. It is desirable to provide tool users with an alternative to replacing all of their tools for use with new toolholder systems.
The present invention permits tool users to use existing tool supplies with new toolholder systems. Moreover, the present invention permits tools to be secured relative to chucks in an accurate fashion that minimizes the possibility of the tools being misaligned relative to an axis of rotation of the tools. Further, the present invention permits use of tools having threads with toolholders having threads that minimizes the potential for damage to the threads.
According to an embodiment of the present invention, a tool extender and tool assembly is provided. The tool includes a first and a second end, a working portion for performing an operation on a workpiece being provided at the first end and a shank extending from the working portion to the second end. The shank includes a bushing, a first guide portion, an externally threaded portion, and a second guide portion arranged successively in a direction away from the working portion. The tool extender includes a first end and a second end. The tool extender includes a substantially cylindrical bore in which the shank is receivable up to the bushing, the bushing abutting against a forward edge of the tool extender at the first end. The bore includes a first internal guide portion, an internally threaded portion for mating with the externally threaded portion, and a second internal guide portion arranged successively in a direction toward the second end of the tool extender. The tool and the tool extender are shaped such that, when the bushing abuts against the forward edge of the tool extender and the internally threaded portion and the externally threaded portion are mated, the first guide portion and the second guide portion are disposed adjacent the first internal guide portion and the second internal guide portion of the bore.